Suction compressor temperature regulator device for transcritical and subcritical r-744 compressors

ABSTRACT

A suction compressor temperature regulator device, for use with at least one compressor of a R-744 refrigeration system, includes a heating mechanism located upstream of the at least one compressor of the refrigeration system, in a suction line thereof, for locally controlling the temperature of a R-744 fluid of the refrigeration system. The heating mechanism is typically in a form of a heat exchanger connected to the suction line and using a heating fluid to transfer heat therefrom to the R-744 fluid at the heat exchanger.

CROSS REFERENCE TO RELATED APPLICATION

Benefit of U.S. Provisional Application for Patent Ser. No. 61/457,817filed on Jun. 10, 2011, which is incorporated herein by reference, ishereby claimed.

FIELD OF THE INVENTION

The present invention concerns refrigeration systems and methods, andmore particularly a suction compressor temperature regulator device fortranscritical and subcritical R-744 compressors in R-744 refrigerationsystems.

BACKGROUND OF THE INVENTION

Refrigeration systems are commonly used in supermarkets to refrigerateor to maintain in frozen state perishable products, such as foodstuff.

Presently the R-744 subcritical refrigeration systems are defrostedelectrically for the low temperature applications and by air defrost forthe medium temperature applications.

Furthermore, the suction temperature of R-744 compressors (subcriticalor transcritical) is required to be maintained at a level at least 36°F. higher than the evaporating temperature in order to avoid oil foamingand to achieve reliable and stable operation. This is extremelydifficult to achieve by the habitual methods used in Freon™ systems. Themost common method used is suction to liquid heat exchanger. However inthe case of R-744 system the liquid temperature is very low (around 20°F.) and is inappropriate for use in such heat exchanger. It would bealso difficult to regulate the liquid flow rate through the heatexchanger in order to achieve stable suction temperature at the requiredlevel.

Accordingly, it would be desirable to have an improved suctioncompressor temperature regulator device for transcritical andsubcritical R-744 compressors for refrigeration systems.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved suctioncompressor temperature regulator device for transcritical andsubcritical R-744 compressors for refrigeration systems.

An advantage of the present invention is that the suction compressortemperature regulator device is simple and allows the correspondingcompressor(s) to substantially remain within efficient operatingconditions, as possible, by controlling the temperature of the R-744fluid reaching the compressor(s). The heating mechanism of the device istypically regulated by a temperature sensor sensing the temperature ofthe R-744 fluid located between the heating mechanism and thecompressor(s).

According to an aspect of the present invention, there is provided asuction compressor temperature regulator device for use with at leastone compressor of a R-744 refrigeration system, said device comprising:

-   -   a heating mechanism located upstream of the at least one        compressor of the refrigeration system, in a suction line of the        at least one compressor for locally controlling the temperature        of a R-744 fluid of the refrigeration system.

In one embodiment, the heating mechanism is in a form of a heatexchanger connected to the suction line and using a heating fluid,wherein heat from the heating fluid is transferrable to the R-744 fluidat the heat exchanger.

Conveniently, the heating mechanism includes a heating fluid circuitwith heating fluid modulating valve regulating a rate of heating fluidcirculating through the heat exchanger.

Typically, the modulating valve is controlled by a temperature of theR-744 fluid flowing in the suction line between the heat exchanger andthe at least one compressor.

Preferably, the heating fluid circuit includes a pressure regulatingvalve located downstream of the modulating valve and upstream of theheat exchanger.

In one embodiment, the at least one compressor is a transcriticalcompressor, the suction line is a transcritical suction line, the heatexchanger is a transcritical heat exchanger, and the heating fluidmodulating valve is a transcritical heating fluid modulating valve; theheating fluid circuit of the device further including a subcriticalheating fluid modulating valve regulating a rate of heating fluidcirculating through a subcritical heat exchanger connected to asubcritical suction line of at least one subcritical compressor fortransferring heat to the R-744 fluid thereat.

Conveniently, the subcritical modulating valve is controlled by atemperature of the R-744 fluid flowing in the subcritical suction linebetween the subcritical heat exchanger and the at least one subcriticalcompressor.

Typically, the pressure regulating valve is located downstream of thetranscritical and subcritical modulating valves and upstream of thetranscritical and subcritical heat exchangers.

In one embodiment, the heating fluid circuit is part of a heat reclaimcircuit of the refrigeration system.

Conveniently, the heating fluid reaches the heat exchanger beforereaching a heat recuperator of the heat reclaim circuit.

Typically, the heat recuperator is located between the at least onecompressor and a gas cooler of the refrigeration system such that heatfrom the compressed R-744 fluid is transferred to the heating fluid ofthe heat reclaim circuit.

In one embodiment, the heating mechanism is in a form of an electricalheating device located at the suction line for transferring heat to theR-744 fluid thereat.

According to an aspect of the present invention, there is provided aR-744 refrigeration system having at least one compressor and a suctioncompressor temperature regulator device as claimed in claim 1 for usetherewith.

Other objects and advantages of the present invention will becomeapparent from a careful reading of the detailed description providedherein, with appropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects and advantages of the present invention will becomebetter understood with reference to the description, provided forpurposes of illustration only, in association with the following figure,wherein:

FIG. 1 is a schematic diagram of a suction compressor temperatureregulator device for transcritical and subcritical R-744 compressors inR-744 refrigeration systems, in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, there is shown a simplified R-744 transcritical refrigerationsystem 101 with a heat reclaim capabilities using a glycol solution asheat transfer fluid, incorporating an embodiment of a suction compressortemperature regulator device 100 for transcritical and subcritical R-744compressors in accordance with the present invention.

In the suction line 1′ of the transcritical compressors 1 of therefrigeration system 101, the suction compressor temperature regulatordevice 100 includes a heating mechanism that is preferably in the formof a heat exchanger 4 that is connected through conduit 9 and throughmodulating valve 14 to conduit 15, and through conduit 8 to conduit 16after the pressure regulating valve 10 of a heat reclaim circuit 11having atypical recuperator 5 used to cool down the hot gas downstreamof the compressors 1 (and provide comfort heating for the building (notshown) at the same time, or the like) before the gas reaches the gascooler 6, thus allowing a warm glycol solution or the like to flowthrough heat exchanger 4 at a controlled rate. The flow rate of the warmglycol solution is typically regulated by modulating valve 14 and iscontrolled by the temperature, via a temperature sensor (not shown) orthe like, of the R-744 fluid vapours between heat exchanger 4 andcompressor 1.

Similarly, in the suction line 2′ of the subcritical compressors 2 ofthe refrigeration system 101, the suction compressor temperatureregulator device 100 includes the heating mechanism that is preferablyin the form of a heat exchanger 3 that is connected through conduit 7and through modulating valve 13 to conduit 15, and through conduit 8 toconduit 16 after the pressure regulating valve 10, thus allowing a warmglycol solution or the like to flow through heat exchanger 3 at acontrolled rate. The flow rate of the warm glycol solution is typicallyregulated by modulating valve 13 and is controlled by the temperature,via another temperature sensor (not shown) or the like, of the R-744fluid vapours between heat exchanger 3 and compressor 2.

Although not shown, it would be obvious to one skilled in the art thatany other warm fluid solutions could be considered to be used with theheat exchangers 3 and 4, or even different types of heating mechanismfor controlled local heating, such as electrical heating device 3′ orthe like, of the fluid just upstream (in the suction line) of thetranscritical 1 and/or subcritical 2 compressors, and preferablycontrolled by the temperature, via a temperature sensor (not shown) orthe like, of the R-744 fluid vapours inside the suction line 2′ justupstream of the compressor 2, without departing from the scope of thepresent invention.

Although the present invention has been described with a certain degreeof particularity, it is to be understood that the disclosure has beenmade by way of example only and that the present invention is notlimited to the features of the embodiments described and illustratedherein, but includes all variations and modifications within the scopeand spirit of the invention as hereinafter claimed.

1. A suction compressor temperature regulator device for use with atleast one compressor of a R-744 refrigeration system, said devicecomprising: a heating mechanism located upstream of the at least onecompressor of the refrigeration system, in a suction line of the atleast one compressor for locally controlling the temperature of a R-744fluid of the refrigeration system.
 2. The device of claim 1, wherein theheating mechanism is in a form of a heat exchanger connected to thesuction line and using a heating fluid, wherein heat from the heatingfluid is transferrable to the R-744 fluid at the heat exchanger.
 3. Thedevice of claim 2, wherein the heating mechanism includes a heatingfluid circuit with heating fluid modulating valve regulating a rate ofheating fluid circulating through the heat exchanger.
 4. The device ofclaim 3, wherein the modulating valve is controlled by a temperature ofthe R-744 fluid flowing in the suction line between the heat exchangerand the at least one compressor.
 5. The device of claim 4, wherein theheating fluid circuit includes a pressure regulating valve locateddownstream of the modulating valve and upstream of the heat exchanger.6. The device of claim 5, wherein the at least one compressor is atranscritical compressor, the suction line is a transcritical suctionline, the heat exchanger is a transcritical heat exchanger, and theheating fluid modulating valve is a transcritical heating fluidmodulating valve; the heating fluid circuit of the device furtherincluding a subcritical heating fluid modulating valve regulating a rateof heating fluid circulating through a subcritical heat exchangerconnected to a subcritical suction line of at least one subcriticalcompressor for transferring heat to the R-744 fluid thereat.
 7. Thedevice of claim 6, wherein the subcritical modulating valve iscontrolled by a temperature of the R-744 fluid flowing in thesubcritical suction line between the subcritical heat exchanger and theat least one subcritical compressor.
 8. The device of claim 7, whereinthe pressure regulating valve is located downstream of the transcriticaland subcritical modulating valves and upstream of the transcritical andsubcritical heat exchangers.
 9. The device of claim 5, wherein theheating fluid circuit is part of a heat reclaim circuit of therefrigeration system.
 10. The device of claim 9, wherein the heatingfluid reaches the heat exchanger before reaching a heat recuperator ofthe heat reclaim circuit.
 11. The device of claim 10, wherein the heatrecuperator is located between the at least one compressor and a gascooler of the refrigeration system such that heat from the compressedR-744 fluid is transferred to the heating fluid of the heat reclaimcircuit.
 12. A R-744 refrigeration system having at least one compressorand a suction compressor temperature regulator device as claimed inclaim 1 for use therewith.
 13. The device of claim 1, wherein theheating mechanism is in a form of an electrical heating device locatedat the suction line for transferring heat to the R-744 fluid thereat.